A switching power supply circuit includes an intermittent oscillation control circuit, which performs intermittent oscillation control that repeats a cycle including an oscillation time period and a stop time period according to a feedback signal so that output voltage or current becomes constant, compares an intermittent oscillation period that is a sum of the oscillation time period and the stop time period with a preset target period, sets the oscillation time period of current cycle to a length obtained by extending the oscillation time period of previous cycle by first predetermined time when the intermittent oscillation period is shorter than the target period, and sets the oscillation time period of current cycle to a length obtained by subtracting second predetermined time from the oscillation time period of previous cycle when the intermittent oscillation period is longer than the target period, in each cycle of intermittent oscillation control.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A switching power supply device, comprising: an energy conversion circuit to which an input voltage is input, the input voltage being a direct current input voltage; a rectifying and smoothing circuit that rectifies and smooths a voltage output from the energy conversion circuit, and outputs an output voltage to a load; a switching element connected to the energy conversion circuit, the switching element switching the input voltage; a switching control circuit that controls switching operation of the switching element; and an output state detection circuit that outputs a feedback signal in accordance with one of the output voltage and an output current flowing through the load, wherein: the switching control circuit includes an intermittent oscillation control circuit that performs intermittent oscillation control in which a cycle including an oscillation time period in which the switching element performs switching operation and a stop time period in which the switching operation stops is repeated in accordance with the feedback signal so that one of the output voltage and the output current becomes constant, and the intermittent oscillation control circuit includes a first comparator that determines whether the oscillation time period is to be started, according to the feedback signal, and a second comparator that compares an intermittent oscillation period that is a sum of the oscillation time period and the stop time period with a target period that is preset, sets the oscillation time period of a current cycle to a length obtained by extending the oscillation time period of a previous cycle by a first predetermined time when the intermittent oscillation period is shorter than the target period, and sets the oscillation time period of the current cycle to a length obtained by subtracting a second predetermined time from the oscillation time period of the previous cycle when the intermittent oscillation period is longer than the target period, in each cycle of the intermittent oscillation control.
2. The switching power supply device according to claim 1 , wherein: the intermittent oscillation control circuit sets the oscillation time period of the current cycle by comparing, by using the second comparator, a voltage of a capacitive element that is charged or discharged from start of the oscillation time period of the current cycle and an oscillation time period setting voltage; and the oscillation time period setting voltage increases or decreases from a voltage value of the capacitive element stored when the oscillation time period of the previous cycle terminates by a predetermined voltage amount corresponding to one of the first predetermined time and the second predetermined time.
3. The switching power supply device according to claim 1 , wherein one of the first predetermined time and the second predetermined time is set within a range of from ½ times to two times a switching operation period of the switching element.
4. The switching power supply device according to claim 1 , wherein one of the first predetermined time and the second predetermined time is set in accordance with a count amount of the number of times of the switching operation of the switching element.
5. The switching power supply device according to claim 4 , wherein the count amount is one.
6. The switching power supply device according to claim 1 , wherein the intermittent oscillation control circuit includes an intermittent oscillation period modulator that periodically changes the intermittent oscillation period within a range of from a first period to a second period.
7. The switching power supply device according to claim 6 , wherein the intermittent oscillation period modulator periodically changes the target period within a range of from a third period to a fourth period that are preset.
8. The switching power supply device according to claim 7 , wherein: the intermittent oscillation period modulator changes the target period each time the intermittent oscillation period reaches the target period; and the target period is alternately changed to one of the third period and the fourth period.
9. The switching power supply device according to claim 6 , wherein the intermittent oscillation period modulator periodically changes a threshold value for setting a peak value of current flowing through the switching element within a range of from a first threshold value to a second threshold value that are preset.
10. A semiconductor device for the switching power supply device according to claim 1 , the semiconductor device comprising: a semiconductor substrate; and the switching control circuit in the switching power supply device disposed as an integrated circuit on the semiconductor substrate.
11. A semiconductor device for controlling a switching element connected to an energy conversion circuit, the semiconductor device comprising: a semiconductor substrate; and a switching control circuit that controls switching operation of a switching element and is disposed as an integrated circuit on the semiconductor substrate, wherein: the switching control circuit includes an intermittent oscillation control circuit that performs intermittent oscillation control in which a cycle including an oscillation time period in which the switching element performs switching operation and a stop time period in which the switching operation stops is repeated in accordance with a feedback signal output from an output state detection circuit in accordance with one of the output voltage and an output current flowing through a load so that one of an output voltage of a rectifying and smoothing circuit and the output current becomes constant, and the intermittent oscillation control circuit includes a first comparator that determines whether the oscillation time period is to be started, according to the feedback signal, and a second comparator that compares an intermittent oscillation period that is a sum of the oscillation time period and the stop time period with a target period that is preset, sets the oscillation time period of a current cycle to a length obtained by extending the oscillation time period of a previous cycle by a first predetermined time when the intermittent oscillation period is shorter than the target period, and sets the oscillation time period of the current cycle to a length obtained by subtracting a second predetermined time from the oscillation time period of the previous cycle when the intermittent oscillation period is longer than the target period.
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February 22, 2019
April 21, 2020
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